The present invention relates to an antimicrobial (antibacterial) glass capable of releasing an Ag ion and a manufacturing method thereof, and more particularly to an antimicrobial glass which is excellent in dispersibility into a resin or in transparency and a manufacturing method thereof.
Recently, in the field of construction material, home electric appliances (including television sets, personal computers, portable telephones, video cameras and the like), sundries, packaging material and the like, to give an antimicrobial effect, an antimicrobial resin composition which is produced by mixing a given amount of antimicrobial glass into a resin has been used.
As such antimicrobial glass, a glass water treatment agent which is capable of resolving Ag ion therein is disclosed in JP62(1987)-210098A.
This glass water treatment agent is formed of boron silicate based antimicrobial glass which contains 0.2-1.5 parts by weight of mono valent Ag ion based on silver oxide conversion per 100 parts by weight of glass and also contains 20-70 mol % of B2O3 as a glass component. To be more specific, in examples 2 and 3 of this patent publication, the antimicrobial glass containing 20-30 mol % of B2O3, 40 mol % of ZnO, 30-40 mol % of P2O5 and 1 weight % of Ag2O is disclosed.
Further, in JP01(1989)-313531A, as the antimicrobial resin composition, a synthetic resin molded body containing antimicrobial glass into a resin is disclosed. To explain this synthetic resin molded body specifically, the synthetic resin molded body includes anti microbial glass containing 0.1-20 parts by weight of Ag2O as mono valent Ag in 100 parts by weight of glass solid formed of one, two or more kinds of network-forming oxides selected from a group consisting of SiO2, B2O3, P2O5 and one, two or more kinds of network-modifying oxides selected from a group consisting of Na2O, K2O, CaO, ZnO into a resin. To be more specific, in the embodiment of the above-mentioned patent publication, there is disclosed antimicrobial glass which adds 2 parts by weight of Ag20 to 100 parts by weight of mixture formed of 40 mol % of SiO2, 50 mol % of B2O3 and 10 mol % of Na2O.
However, the antimicrobial glass disclosed in JP62 (1987) -210098A contains 20-70 mol % of B2O3 as glass composition. Further, although it is considered that the shape is not taken into account, the antimicrobial glass is whitened or reflocculated so that there has been a problem that the antimicrobial glass exhibits poor transparency and is liable to generate yellowing. Further, there has been also a problem that when the antimicrobial glass is mixed into a resin, the dispersibility of the antimicrobial glass is insufficient.
Accordingly, when the antimicrobial glass which exhibits the poor transparency and the poor dispersibility is mixed into a resin or laminated to a surface of a resin molded product, there has been a problem that color and transparency that the resin per se has are damaged or the resin molded product exhibits poor surface smoothness.
Further, the antimicrobial glass disclosed in JP01(1989)-313531A contains B2O3 as a main component. Further, in this antimicrobial glass, compounding amounts of network-forming oxide and network-modifying oxide are not optimized. Still further, there has been a problem that since the shape is not taken into consideration, the antimicrobial glass exhibits poor transparency and poor dispersibility or generates yellowing. Still further, there has been a problem that such antimicrobial glass requires an excessively long manufacturing time due to glass composition thereof.
Accordingly, the applicant has already proposed in JP2000-191339A, a dissoluble glass with little yellowing which substantially does not contain B2O3 but contains Ag2O, ZnO and P2O5 instead, wherein assuming a total amount to 100 weight %, a content of Ag2O is set to a value within a range of 0.2 to 5 weight %, a content of ZnO is set to a value within a range of 1 to 50 weight %, and a content of P2O5 is set to a value within a range of 30 to 80 weight %.
Although the disclosed dissoluble glass has an advantageous effect that yellowing thereof is small, the compounding amounts of ZnO and network-forming oxide (CaO) are not optimized. Accordingly, when a relatively large amount of ZnO is added and the ZnO amount is fluctuated, there has been a problem that the anti microbial glass exhibits poor transparency and poor dispersibility.
Accordingly, as a result of extensive studies, the inventors have found that by limiting the shape and average particle size of the antimicrobial glass respectively, even when the antimicrobial glass contains no ZnO, or the antimicrobial glass contains a relatively large amount of ZnO, or the antimicrobial glass contains a given amount of B2O3, the antimicrobial glass exhibits small yellowing and it is possible to enhance transparency and dispersibility of the antimicrobial glass.
That is, the inventors have found that irrespective of the glass composition, it is possible to obtain the antimicrobial glass which can be easily manufactured while exhibiting small yellowing and excellent transparency and dispersibility and have completed the present invention.
According to the present invention, there is provided an antimicrobial glass capable of releasing an Ag ion which is characterized in that the antimicrobial glass has the shape of a polyhedron and also has an average particle size set to a value in the range of 0.1 to 300 xcexcm and the antimicrobial glass can solve the above-mentioned problems.
That is, since the antimicrobial glass has the shape of a polyhedron, an amount of progressing light which is impeded by the antimicrobial glass is small. Further, since the antimicrobial glass is hardly reflocculated (coagulated), it is possible to enhance the transparency of the antimicrobial glass per se.
Further, since the antimicrobial glass has the shape of a polyhedron, when the antimicrobial glass is mixed and dispersed into a resin, the antimicrobial glass can be easily oriented in one fixed direction so that the antimicrobial glass is present uniformly into a resin and it is possible to effectively prevent light scattering derived from the antimicrobial glass into a resin.
Further, since the shape of the antimicrobial glass is a polyhedron and an average particle size is restricted to a given range, the dispersing ability of the antimicrobial glass into a resin may be enhanced.
Further, an another mode of the present invention is directed to a method for producing anti-microbial glass which is characterized by comprising following steps (A) to (C).
(A) a step in which glass material containing at least Ag2O is melted to form a glass melt.
(B) a first grinding step in which the glass melt is ground into rough-ground glass having an average particle size exceeding 300 xcexcm.
(C) a second grinding step in which the glass material is ground into coarsely ground glass having an average particle size in a range of 0.1 to 300 xcexcm and having the shape of a polyhedron.
By producing the antimicrobial glass in this manner, it is possible to effectively obtain the antimicrobial glass which exhibits excellent transparency and dispersibility.